[W]hether Council Directive 79/7 EEC precludes the imposition in national law of a requirement that, in addition to satisfying the physical, social and psychological criteria for recognising a change of gender, a person who has changed gender must also be unmarried in order to qualify for a state retirement pension.

As permitted by the Directive, Britain allowed women to obtain a retirement pension at an earlier age than men. However a transgender woman needed a full gender recognition certificate to qualify for the earlier pension, and under British law at the time could not obtain one if she remained married. The facts of the case are summarized in the Court's press release:

So far as MB was concerned, she was registered at birth as a man but has lived as a woman since 1991 and underwent gender reassignment surgery in 1995. She has not applied for a full gender recognition certificate because she and her wife are married and wish to remain so.... On 31 May 2008, MB turned 60 [and] ... applied for a state retirement pension.... That application was rejected....

EurActiv reports on the decision. [Thanks to Paul deMello for the lead.]